A fungus among us

We have a fungus on the trunks of our trees. It is on them all. Makes no
difference what kind of tree. A recent visitor said it would kill all the
trees. How do we get rid of fungus? I do not know how to describe it, but I
have seen the same thing on trees everywhere. Kinda looks like moss wrapped
very tight around the tree. Could someone help out with the what, where and
when. Thanks.
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That's my story and I'm stickin to it!!!
JC down in Gnat Flats, Texas